This proposal requests grant of computing time for the development and enhancement of the analytical capabilities needed to improve the understanding of the biomechanical-biological interactions that form the basis of the musculoskeletal system's adaption to its mechanical environment. The underbar multi-year projects which are currently in progress in which the analytical capabilities would be directly applied include the following: 1. An analysis of biomechanical factors influencing bone remodeling in a canine total hip replacement model. 2. To analyze factors influencing bone ingrowth into porous materials and the micromotion associated with elastic displacement incompatibilities at the interface between porous materials and the host bone. 3. To study adaptive bone remodeling with the help of computer simulations of bone-implant configuration and to find out specifically the consequence of the initial bone geometry and stiffness on adaptive response to the implant. 4. To study geometrical and physical factors that affect the life of an ultra high molecular polyethylene tibial component. 5. To study factors influencing strain and deformation both in the healthy and in the degenerated intervertebral motion segment of the lumber spine. Preliminary studies on these projects have been conducted with the help of finite element models on CRAY Y-MP at UIUC. They helped to understand the effect of some of the important variables on the biological problems considered. Studies have to be conducted on several other variables in all these projects before a clear understanding of the biomechanical-biological interactions can be understood.